[SpringBoot Usage] SpringBoot (3)配置文件及其相关标签使用 (@ConfigurationProperties/@Value/Environment)

前言

在使用SpringBoot的过程中, 总免不了的是其相关配置文件的使用. 我们可以通过, @ConfigurationProperties和@Value标签将applicaiton.properties配置内容注入. 也可以通过Environment对象实时获取. 如下即介绍一下这几种使用方式的优缺点和基本实现.

前置

pom.xml

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <springboot.version>2.3.12.RELEASE</springboot.version>
        <lombock.version>1.18.12</lombock.version>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        
    </dependencies>

笔者这边使用父子maven项目的模式. 相关版本还请各位读者自己维护一下。

application.yml

server:
  port: 8080
  servlet:
    context-path: /arsenal-springboot

config:
  env:
    name: hello
    age: 18

本次我们只配置通用的配置文件. 不考虑prefix等场景.

标签配置-实战

@Value标签

源码定义

package org.springframework.beans.factory.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Value {
    String value();
}

根据@value标签的定义可知, 其可以配置在FIELD/METHOD/PARAMETER/ANNOTATION_TYPE上面.

测试配置

package com.yanxml.arsenal.springboot.env.config.value;

import lombok.Data;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
@Data
public class StuValue {
    public final static String BEAN_NAME = "StuValue";
    @Value("${config.env.name}")
    private String name;
    @Value("${config.env.age}")
    private Integer age;
}

此处使用绑定属性的方式.

测试获取

@RestController
@RequestMapping(value = "env")
public class EnvController {

    @Autowired
    private StuValue stuValue;
 
    @RequestMapping(value = "stuValue", method = RequestMethod.GET)
    @ResponseBody
    public Object getStuValue(){
        return stuValue;
    }

 }

在这里插入图片描述

@ConfigurationProperties 标签

package org.springframework.boot.context.properties;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.core.annotation.AliasFor;
import org.springframework.stereotype.Indexed;

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Indexed
public @interface ConfigurationProperties {
    @AliasFor("prefix")
    String value() default "";

    @AliasFor("value")
    String prefix() default "";

    boolean ignoreInvalidFields() default false;

    boolean ignoreUnknownFields() default true;
}

测试用例

package com.yanxml.arsenal.springboot.env.config.configuration;

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties(prefix = "config.env")
@Data
public class StuConfiguration {
    public final static String BEAN_NAME = "StuConfiguration";
    private String name;
    private Integer age;
}

此处值得注意的是@ConfigurationProperties需要和@Component标签一同使用.

@RestController
@RequestMapping(value = "env")
public class EnvController {
    @Autowired
    private StuConfiguration stuConfiguration;

    @ResponseBody
    @RequestMapping(value = "stuConfiguration", method = RequestMethod.GET)
    public Object getStuConfiguration(){
        return stuConfiguration;
    }

}

在这里插入图片描述

Environment实时获取

如果我们看过Spring的装载过程, 即可知道. Spring在装载时, 获取环境变量和相关配置文件, 并且将其放入Environment对象内. 我们可以通过get()方法获取其中的各个对象.

测试用例 - StuEnv

package com.yanxml.arsenal.springboot.env.config.environment;

import lombok.Data;

@Data
public class StuEnv {
    public final static String BEAN_NAME = "StuEnv";
    private String name;
    private Integer age;
}

测试用例 - StuEnvConfig

package com.yanxml.arsenal.springboot.env.config.environment;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Component;

@Component
public class StuEnvConfig {
    @Autowired
    private Environment environment;

    @Bean
    public StuEnv generateStuEnv(){
        StuEnv stuEnv = new StuEnv();
        stuEnv.setName(environment.getProperty("config.env.name"));
        stuEnv.setAge(Integer.valueOf(environment.getProperty("config.env.age")));
        return stuEnv;
    }
}

此处值得注意的是, @Bean标签修饰的方法, 需要是一个public类型的方法.

测试用例 - controller

@RestController
@RequestMapping(value = "env")
public class EnvController {
    @Autowired
    private StuEnv stuEnv;


    @RequestMapping(value = "stuEnv", method = RequestMethod.GET)
    @ResponseBody
    public Object getStuEnv(){
        return stuEnv;
    }
}

在这里插入图片描述

配置文件注意事项1 - prefix前缀

配置文件注意事项2 - 配置文件的指定优先级 & 如何运行时强行指定

@ConfigurationProperties装配原理和自定义实现

TODO 敬请期待下一篇博客.

Reference

[1] @ConfigurationProperties使用详解
[2] (Offical)(2.3.12.RELEASE)configuration-metadata-annotation-processor